One thing I can tell you, is that my mechanical knowledge of this car is zilch. I just bought it a few months ago and i've been more concerned with restoring the asthetics than worrying about anything else since it was running quite well. Before long though, I realized I was barely getting 100 miles a tank with mostly city driving. That definitely was not what i was bargaining for:

What I do know is this:

1. The engine was recently rebuilt- about 15K miles ago
2. Performance Headers were put on it at that time
3. A performance Carb i think was also put in at that time, but i'm not sure. The previous owner didn't do anything with it either, but he did tell me he was sure it needed tuned.

I read the 5 year old thread about a 84 t/a having similar issues, and I asked my car guy about the possibility of MPG over 20. He laughed in my face, and said there was no way, and I shouldn't expect much more than 10 with what i've got, and I think that's ridiculous. He said other than doing a engine switch to a stock engine, i wouldn't see much more than maybe 12 or so. To me that's unacceptable, so I'd love to hear what everyone thinks could be areas I could check for problems, or things to have tweaked which could get me somewhere close to 15 at least so I can drive this thing without hating myself.

 

Probably jetted wrong. Mine is warmed up and gets 18-22 with the 305 in it.

 

So what should I have done to correct it?

 

If this other carb isn't computer-controlled, that's most likely at the core of the problem.

If the distributor wasn't downgraded at the same time as the carb, that'd be the VERY FIRST thing to take care of.

Get a good quality one WITH MECHANICAL AND VACUUM ADVANCE.

 

Thanks! The question is- how would I know and how can i tell?

 

This is the first car i've ever had in my life with a carb, so i'm way more ignorant than usual

 

its probbly unning rich, take it someone who knows carbs like thaback of their hand and have them tune it. the dist wont be a huge problem but it wont help much either. if you went with the vacuum and and machanial advance youd be a million times better. ive gotten decent mileage with all my thhirdgens even the ones that ran wrong and burned rich.

 

That would be, someone like me...

A distributor with vacuum advance will have a big can thing with a vacuum lone hanging off the side of it. No that, ... won't work well with the computer disabled.

Should be something like this. Not this particular one necessarily, just, one that has this one obvious feature.

http://www.summitracing.com/parts/sum-850001r/overview/

If it doesn't have that, don't bother with anything else until you get one that does.

20 mpg is easy; these cars got a good bit better than that when new.

 

I had a '78 Camaro 350 that had the 5" tall rear spoiler, 235/60R15s, 3.08:1 axle, and I swapped a 700R-4 with 18:43 speedometer gears, and used #416 heads with L69 intake manifold on GM 0.028" head gaskets. Very first road trip, SLC, UT toward Green River, UT, averaging 65 MPG got me 25.1 MPG with the centrifugal advance stuck at zero. Initial was 6* and vacuum advance was 20*, cat-back was upgraded to mandrel-bent single 2.25". Copy that into your sleeker car, with a fully functional HEI, and slow down to 60 MPH, you should do 28 MPG.

 

Ah! Well how would I know if the computer is disabled? I'll definitely check to see what mine looks like. And i'll search the greater jacksonville area for a carb expert lol

 

Best place to find a carb tuner is an old car show. If u ask nicely, an older hot rodder will point u to someone. That's how I had my 85 done. Before the expert checked it over I was getting maybe 15 mpg with a stockish 400 SBC. After I recorded 24 hwy. 18 street. Hope that helps.

 

if the computer is still active,you should have a "check engine"light that comes on when ignition switched on and goes out shortly after engine started-presuming no trouble codes present.

 

If the carb doesn't have 2 electric connectors plugged into it at the front, it's ... fornicated.



Here's a computer-controlled one. Note the plugs with multiple wires each, at the top left and bottom right of the pic. If your "performance" carb downgrade doesn't have that, then your computer is effectively disabled; and if you don't have the right kind of distributor, you need one BEFORE even thinking about messing with the carb.

 

If you don't know anything about carbs, emission controls or tuning you might consider a shop that can set it up for you. Jetting, distributor tuning (advance, curve and base setting) all take years of experience to set up correctly.

OTH you have many years of experience and many opinions here.....Look at SOFA's pic...does your carb look just like that? Does the distributor have a silver can on the base of it? Is the ck eng lamp on in the dash? Numbers from the carb, dist, and motor can tell us what you actually have....provide some pics and we can work through it.

 

Here's a pic- hopefully this is what you guys needed to see. it was hard to get the photo down to 1mb, my camera is too nice! It doesn't look like there are two plugs in mine.....and there is no check engine light when i go to start up the car.

 

So you do not have a computer controlled carb.
Now you need to check the distributor. For a non computer carb you need a distributor with a vacuum advance. It will look like a small round can with a nipple on it where a vacuum hose attaches.
should look like this
http://www.jegs.com/i/JEGS+Performan...40005/10002/-1

 

No; not computer controlled.

That's just an Edelbrock carb.

Oh well.

Sorry to see you've been downgraded to a non-compatible setup.

Oh well. We'll do what we can to help you out anyway, as much as possible.

Since it's not the carb the distributor was designed to go with, if you haven't changed that out, it'll NEVER work right.

Get a distributor with centrifugal and vacuum advance in there, and then come back and let's see what we can do.

Until you have that distributor, not much point in any further posts, because none of them (except for "get the right distributor") will be of any value. No matter how earnestly and vigorously the posters protest.

 

A non-computer Q-Jet has the potential to give better MPG than any other carburetor, because that computer control forces a A:F of 14.7:1 for emissions when you really want leaner for more MPG. I think I recall reading something like 16.5:1? But the Edelbrock / Carter doesn't have the triple venturi primaries like the Q. At least the Edelbrock has the easiest tuning, the Holley has far too much you can do, and far too much conflicting information everywhere. Edelbrock offers instructions how to calibrate in 3% increments, so you can keep going leaner until you get surging when cruising, then back up one step.
MPG iusn't just the carburetor adjustment. As you change your fueling you'll need to keep experimenting with ignition timing. A leaner burn is a hotter burn, so you may need to change spark plugs to a different heat range as well. Probably cooler.

 

Is it that much more of a problem to just replace the carb with one which is computer controller? I'm willing to do that if it will make that much of a differenfce

 

My brothers 1980 Vette has a 375 hp 312 in it aka bored .040" over 305, with a crane 272H10 cam and Vortec heads with a victor jr intake and edelbrock 1406 with some metering rod and jet changes by me. I have to stay a little richer due to the airgap style single plane but even with the 2,800 stalled powerglide in the car and 3.07 gears it gets 25 mpg highway with the a/c on.

 

Okay, here is the distributor guys:

Shoot away

 

Ok, that is a mechanical distributor.

 

Comic-Fast: Thanks a lot. Really great information for someone with mechanic knowledge. This is not my area of expertise, I understood about 3 words you guys wrote. Really, what i'm looking for here is: Do i need to replace parts, if so, what do i need to buy, and what do i tell the person working on it so that it is done to give me better MPG. I'm not doing any of this **** myself. My goal is 20 MPG highway, 15 city while still allowing the car to start properly and not stall. I don't care about HP loss as long as it suddenly isn't running like a 1996 Honda Civic. The least expensive ways to accomplish that mix of things, i'm all in, just feed it to me

 

i thought we were looking at the ac as the distributor for a second there.

 

Okay guys- So now we know that replacing the distributor is round 1. Specific product recommendations are welcome. What do I need to buy, and do i need anything besides the distributor itself?

I'm guessing once its replaced, then tuning the carb is round two, or would it then be the best to replace the carb as well.

 

I see a vacuum advance on the distributor, so you shouldnt need to replace it.

Before I started messing with the carb, I would make sure the basic tune up stuff is done.
Spark plugs, distrubutor cap and rotor are all in good shape. Lube the advance weights in the distributor and make sure the timing is set correctly.
This will give you a good starting point to tune the carburetor.

 

I'm not going to be tuning the carb. I don't do mechanical stuff, don't understand timing. again, just trying to figure out what i need to do

 

how could it be tuned so bad that its getting 1/3 of the gas mileage its supposed to get. Should I replace this carb with another one or not?

 

Well then you have a delimna, be satisfied with 12 mpg or learn to tune your ignition and carb.

 

a good old fashioned carburetor and mecanical/vacuum advance distributor is the perfect thing for learning how to tune a car...

you need a few tools:
vacuum gauge
timing light- i LOVE my Craftsman dial back light... just set the **** to the timing you want, and turn the distributor until it lines up with the TDC mark...
distributor wrench- well worth the price just so you don't have to try to get a regular wrench down under the distributor to get at the bolt when you want to move the distributor..
flat blade screw driver..

that's it- that's all the tools you need to get the timing set and the carburetor adjusted... call Edelbrock- as in, dial their 800 number and talk to a real person- and i bet they'd send you the tuning book that explains how to set up that carb for free. the manual that came with my 1910 Quadrajet did a pretty thorough job of explaining not only how the carburetor does what it does and how to tweak it, but also the role of the ignition system and how to tweak that, too..
then just start hanging around wherever the older car guys hang out- they would be more than happy to help you get your car dialed in and teach you what you need to know. look for the greasy 60 year old guy with the beard in the beat up jalopy that runs 100 times better than it looks like it should- he's probably the guy that can teach you the most, even if the car's a late 60's Ford product..

 

You've taken 2 pics of the AC accumulator up there in post 21. By chance, the dizzy is visible up the back of the first pic, and does have a vac canister. So correct dizzy for a non-cc carb.

Then do basic tune-up stuff as outlined by Joshc in post 26.

Then you'll HAVE to learn how to tune it, as pointed out by Fast in post 29. No getting around it, either you or someone else, but has to be done.

 

I noticed in the picture that shows the vacuum advance....Its hitting the intake manifold. I bet the distributor was stabbed 1 tooth retarded and doubt he is getting enough initial timing.

 

Hey yeah - well spotted! Agree

 

Not sure what the op is after...
He asks for advise, then when he is given advise, he just say, I dont know anything about cars.
Either learn to work on your car or pay someone else to do it. Simple as that.
Your getting 12mpg city with a v8 car, You probably won't get much more than 15-16 city with it even when properly tuned.

 

Really, everyone...thanks! Its really simple. I don't mind paying someone to fix it, that is actually my plan. I just want to know what needs to be done. If something needs replaced, i'll replace it. I want the most fuel efficient car possible. I just know that when you take a car to get fixed, you get a million different BS answers and i'm trying to figure out what needs to be done on mine specifically in order to make that happen.

We now know the distributor and carb i have. So.....should i replace them with something else or keep them to maximize the MPG? If I should keep them, is there anything other than tuning the carb and doing a good ole fashion tune up that can be done? When doing the tuneup, what specific products/brands should I buy to make sure I don't have low quality garbage in my car.

And FYI- I have the edelbrook carb book, and i read it weeks ago. Don't understand a damn thing it tells me, so i'm definitely not doing this myself. I don't even live in an area where i could work on the car myself if I had to. You are the car guys, not me. Otherwise i wouldn't be here asking for help right?

 

Josh- I'm getting 7 MPG, not 12. 5 Guys on this board so far said i could easily get 20 MPG. Maybe if everyone could get on the same page, I'd be able to figure out what to do. What is realistic? I'd really like to get 20, i'd settle for 15-17

 

Fast- thanks for noticing that, so do i need a new one, get it tested, what?

 

an entire tank of gas lasted me exactly 106 miles to empty, so there you go

 

Get it timed properly after removing it and checking the bushings for excess play. You should also ensure the centrifical advance mechanism operates properly and is not worn in any way. The weights have a tendency to wear at the pivot points. It should also be noted that you can buy a kit with necessary springs to adjust the centrifical advance to your exact setup. The vacuum advance can on the side of the distributor is also available in an adjustable design that allows adjustment of both the rate and total amount of vacuum advance. There is much more to a distributor than just base timing alone.

 

Your problem is the carb. get a Holley 4150 with vac secondaries and 600 cfm, Change the rotor in the distributor and set the timeing with the vac line disconected to 10 before top dead center. You want one with the electric automatic choke. Those Carter carbs ie Edelbrock, have floats that sink and needles that stick and sometimes the housing will heat warp. Why Vic bought the rights to build them is beyond me. I use to run Mopars that came stock with them and the first mod I would do would be to put a Holley on. Holleys are simple to set up and tune. Out of the box the 600 4150 will run better than your Edelbrock before you tune.

Mileage as bad as yours can only be the carb went south and it is not worth fixing.

 

You can't fix this by throwing a new carburetor and a new distributor on a mystery engine with a mystery camshaft. Even the computer-controlled QuadraJet has adjustments that must be fine-tuned to match each individual engine. Likewise fine-adjusting the initial timing no matter what distributor is installed.
Refusing to learn trial-and-error tuning is fine if you have electronic fuel injection on the engine it came on, and have ability and willingness to pay for dyno-tuning. Otherwise, your refusal is extremely ...what can I type that isn't insulting?... negative.
And the fact is, trial-and-error is what makes it fun to be a real enthusiast. Otherwise, you would be just another adrenaline junky control freak who thinks he / she can drive. That isn't a real enthusiast. That's missing the point entirely.

 

your car isn't complicated.. they were tuning engines like this in the 1940's with only a couple of basic hand tools... yeah, you can pay someone to fix it for you- or you can take a little time to figure out what does what and use the money you save by doing it yourself to buy the tools to do it. and along with that, you get the gratification of knowing that you fixed it and you made it run better.
honestly, if you aren't going to try to get to know how to keep a carbureted car running and how to tune it, then you might as well just get a newer car with efi and be done with it.

 

With Respect guys look at the pictures he has a edelbrock carb and a vac advance dizzy. The problem is the carb. Don't confuse the guy. It is a simple fix if he takes my advice. If the ignition were bad enough to wreck the gas mileage that much the car wouldn't run.

 

Cosmic- I'm not an enthusiast, never claimed to be. I'm a guy with an 82 trans am who wants it to run right, period. Its the same engine that comes stock, it's just rebuilt. I know the headers are
Nova- I'm converting it to KITT, last time i checked that is an 82 trans am, so buying a newer car would kinda defeat the purpose. I know my car isn't complicated, but i'm 34 years old and have never even seen under the hood of a car made before 1991 before this, I don't even recognize the parts. I don't have a solid 6 months to study mechanics magazines, buy hundred of dollars in tools just to figure out how to do this, no offense but i have a demanding job, girlfriend, and other recreational activities that are my hobbies.
mmadden- that's awesome, thank you!!!! That is the kind of specific actionable information I was really looking for.

.....everyone, just humor me for a minute. How hard is it to find a Dyno shop and would type of cost what I typically expect to have someone tune it professionally?

Just so everyone realizes what's going on here, this is one of about 10 issues i'm dealing with and so being judged because i don't have the time to learn the in's and outs of mechanics is really not fair at all. I'm doing all the interior restoration myself and that is what's taking up all my time. I'm doing the carpeting, the seat upholstery, replacing the steering wheel, trying to fix a misaligned hood, a door that suddenly won't open from the inside, and headlights that sometimes close and sometimes don't, and I need to basically completely replace the A/C because both the compressor and the evaporator are leaking badly.

I've already redyed all the interior panels, recovered the headliner with handmade material replaced the seals, the door panels, painted the hubcaps, dyed the back seats, built a bracket to actually allow the A/C to be reconnected in the first place.....and so guys just give me a break okay?

 

A third gen with a carbed v8, I would expect about 15-16 mpg city and 18-21 highway.
Alot of it depends on the particular engine setup.
I prefer the Holley carburetors myself, have a 670 Holley street avenger on my T/A with a 350.
My friend has an Edelbrock 600 on his 84 Camaro with a 305. His car runs good with the Edelbrock, and gets respectable mileage. For all we know your carburetor may have issues like mmadden is referring to. Until someone with some experience and knowledge can look at the car and diagnose the problem, were all just guessing.

 

Madden, i'm going to take your advice because i understand it. Is there anything else at all that I should do (or should be done in general) before or after that, and what expectations should I have for the car once that is done just so i know

 

I doubt the issue is solely the carb. Any good eye will see that the timing can in now way be correctly advanced with the vacuum advance hitting the intake.

I have had very good luck with Edelbrock aka Carter carbs.

NO carb is going to run 100% out of the box either.

I just dialed in an Edelbrock 1406 on a GM 300 HP Crate 350 (Basically an iron head L98 with a hydraulic flat tappet cam) in a 1972 Chevelle Elcamino SS.

As well as an Edelbrock Thunder Series 625 on a 70 Chevy truck that my brother and I swapped Vortecs on the 290 HP GM crate engine. Going to vortecs from the smogger hecho en mexico heads, swapping the intake to an airgap, and dialing in the carb and distributor picked up 60 RWHP @ 5,500.

 

Fair enough Josh- I would be extremely happy with that, dancing in the streets. I wish I had something to do with the engine changes, but even the guy who had the car before me didn't do it, so I have noone to ask what they did. All I was told be the last guy who looked at the car is that with the aftermarket headers and the carb, that I would be lucky to get 10-12 mpg even with a properly tuned carb. He is a good guy and has been working on cars professionally for 20 years, but I don't buy that. Even if I have no clue what you guys are talking about for the most part, you instill me with confidence that it certainly can get definitely north of 15MPG and I just need to find someone who knows enough about this generation of car and tuning. I just find it hard to believe that any tuning could double the mpg, because this isn't something i'd call fine tuning, something is working horrible wrong to be this bad in gas mileage.

Obviously, today....if something isn't working correctly, modern cars give a code and you know its broken. With this car, obviously its not that easy. If the distributor is junk or the carb is junk.........how would anyone know? It starts pretty easy, occasionally stalls at startup but then easily starts the second time. it goes, it has good power, no surging or sputtering. I had absolutely no way of knowing that gas mileage in this 305 would be this poor until i drove it. Oh well

 

So fast, that is an excellent point. When I take this in to get it fixed, how will they address this issue? Is it an easy fix, will something need replaced, or so....what?

 

If you find someone that can properly time the car and it ends up too retarded. Most likely they will just need to remove the distributor cap and rotor, mark its position, and restab it one tooth advanced from its current position. This will allow it to have the proper range of rotation to reach a proper setting. A normal HEI distributor will have 22* of centrifical advance, maybe as much as 24* if it has worn bushings in the mechanism. A 305 is going to like between 28 and 36* total timing. That puts your initial setting somewhere between 4 and 12*, most likely it will like around 10* initial and you will have about 22* centrifical advance for a total of 32* without vacuum.